Amongst the known embodiments of safety brake mechanisms whose structure includes a lever mounted in the driving compartment of the vehicle and operated by the user, whether by hand or by means of a pedal, a self-adjusting device, a self-regulating device and a device which fixes the rest or braking position of the lever when actuated by the user, it should be noted the device disclosed in the Spanish Patent Application No. P 9501758, equivalent to the European Patent Application No. 96923987.0 (EP 0 792 781 A).
The safety brake mechanism described in patent document PCT/ES96/00149 comprises in essence the elements detailed below. A support fixed to the structure of the vehicle and provided with retaining toothing; a brake lever attached by means of a pin for pivoting on the support, which brake lever can pivot between two positions, rest and braking respectively; a ratchet which comprises a lever fixed to the brake lever, the ratchet lever having one of its arms linked to a control device which can be actuated by the user and its other arm having a retaining extension which can mesh with the retaining toothing of the support in order to fix the position of the brake lever; a self-regulating device which comprises a traction body attached to the pivot pin of the brake lever and to which is fixed the corresponding end of the steel cable of the control cable, the traction body being able to pivot around said pin, a thrust body linked to the ratchet and couplable to the traction body during actuation of the brake lever, so that pivoting of the brake lever causes pivoting of the traction body, and a traction spring coaxially mounted with respect to the pivot pin of the brake lever which permanently imparts to the traction body a pivoting motion in the direction of traction of the steel cable; and a self-adjusting device comprising a pin which traverses the support and the traction body, fixing the position of each with respect to the other.
The operation of the safety brake mechanism according to patent document PCT/ES96/00149 is described below. The self-regulating device is supplied ex-works with the traction spring totally compressed; under these conditions, and once the mechanism has been mounted on the vehicle, initial adjustment of the length of the sheathed portion of cable consists in withdrawing the pin which fixes the position of the traction body, in such a way that the latter pivots and subjects the steel cable to traction to the extent required by each particular vehicle. On the basis of said initial adjustment, the self-regulating device then automatically and permanently adjusts the length of said sheathed portion; to that end, when the brake lever is in the rest position the traction spring permanently subjects the steel cable to traction, adjusting the length of its sheathed portion by pivoting of the traction body, so that when the brake lever is moved from the rest position to the braking position, the coupling of the thrust and traction bodies takes place in that position of the traction body for which the portion of sheathed cable is operative under the conditions pre-set ex-works. Fixing the braking position of the brake lever is implemented by meshing the retaining extension of the ratchet lever with the retaining toothing of the support, while passing from the braking position to the rest position is implemented by acting upon the ratchet control device.
The patent document JP-A-09024808 (Patent Abstracts of Japan, Vol. 97, No. 5) discloses a safety brake mechanism for automobile vehicles which includes a support, a brake lever linked to the support, a self-regulating device and a self-adjusting device for length of the portion of the sheathed steel cable, and a device for fixing the position of the brake lever.
In general, the known embodiments of safety brake mechanisms of the type described above have as their main disadvantage that they comprise a large number of components, which considerably increases brake mechanism manufacturing costs.